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Volume 6 Issue 5 (May, 2018)

Original Articles

Microhardness of Flowable Bulk-Fill Composite Materials
Mayyadah Almozainy

Purpose: To evaluate the curing efficiency of various flowable bulk fill resin materials using Vickers hardness measurements and compare them to conventional resin-based composite materialaccording to the manufacturer recommendation time. Materials and method: Four composite materials were used: Tetric N-Ceram, Tetric N-flow Bulk fill, Filtek bulk fill flowable composite and Surefil SDR bulk fill flowable. Six discs of each material were prepared and light polymerized according to the manufacturer recommendation with Bluephase G2 curing unit (Ivoclar Vivadent).Vickers hardness was used to determine microhardness (NOVA 130series, Vickers and Knoop hardness testing instrument) under a 200-gram load and a dwell time of 10 seconds. One-way analysis of variance was used to compare the mean values of the ratio of the bottom and top measurements of tested materials, followed by Tukey’s multiple comparison tests. A p-value of <0.05 was used to report the statistical significance. Results: The mean value of the ratio of the bottom and top measurement shows highly statistically significant difference among the four materials (F=6427.77, p<0.0001) (SDR> Filtek bulk fill flowable> Tetric N-flow Bulk fill> Tetric N-ceram). Conclusion: Manufacturers’ recommendations in regards to curing protocol could result in lower hardness value ratio. Accordingly, the curing time protocol should be longer than that indicated by the manufacturer to achieve 70%- 80% hardness ratio. Subsequently, manufacturers’ recommendation regarding the curing time should be reevaluated and updated based on the results of current literature. Although some of the tested materials exhibit high hardness value, it is still recommended to cap the flowable bulk fill materials with 2mm layer of conventional composite to prevent subsequent water sorption of the composite material. Key words: Composite resins; Bulk-fill; Microhardness.

 
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